Since some of you liked the “truss primer on internal bearings” I did a few weeks ago, I thought I’d try another one. This one is on trusses with cantilevers.
Since we deal mostly with lumberyards, we often get orders called in on small jobs. Anytime we deal with trusses that are cantilevered there seems to be a lot of confusion.
Take an order we got a while back. A customer called in and ordered a handfull of trusses for a room addition. They told the person they were talking to that they needed 20′ trusses cantilevered 2′ one end. The order was processed, and the trusses were built and delivered to the jobsite. But it turns out they were 2′ too short.
Seems the guy had a 20′ wide building, and wanted 22′ trusses. But the details got mixed up in the translation. Now everybody is mad and pointing fingers.
Typically what happens is this: When a lumberyard calls in, they tend to order cantilevered trusses by giving the width of the building and then saying that the trusses are cantilevered. But truss people are conditioned to think of the span of the truss as the length of the bottom chord, and a cantilever means the wall is farther back under the truss. So if neither one questions what the other means, problems result.
I’m not saying either way of thinking is right. But if you get into a situation where you need cantilevered truses, ask questions until you’re sure what you’re getting is what you want.
I can post pics if this isn’t clear to anyone……….
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Replies
I'm surprised you don't supply approval drawings for the customer (lumberyard or contractor) to sign-off. They would obviously have to be dimensionally complete, and possibly show design loads, material, connections, code(s) they are designed to, etc. Or is it not practical for your industry, even though everything is built to order and essentially custom?
Be seeing you...
A couple of problems witht that -
First, it isn't practical to do on every job. This was an order for about $300 worth of trusses.
Second - Many contractors and most homeowners can't understand the shop drawings we print out.
Third - Many of them think if they read shop drawings or give us any info at all, they're accepting more liability.
There is absolutely no substitute for a genuine lack of preparation.
Seems pretty basic to me. If I want a 22' truss cantilevered 2' it better be 22' total width. Never once did the length 24' cross my lips so why should I expect the truss to be 24'. Having been in the custom manufaturing buisness any unclear issues will be used against you. You need to resolve the ordering problem or accept the mis-manufatured product.
It sucks but the customer is always right.
Boss, there must be some control methods lacking in your neck of the woods. I can work with a customer and design a structure that will meet their needs, from the site prep to the ridge vent. An owner, acting as his own GC, could possibly do the same. Then, I used to be able to take my own drawings to the building department, along with the stamped engineered truss drawings, sit down with the plans reviewer for a few minutes and get a permit.
Now, I still design the same structure and get the same stamped truss drawings, but I'm also required to involve a structural engineer who makes his own drawings and calculations which are the only factors the plans reviewer will accept. The structural engineers job is to make sure that the parts of the building, such as the trusses, are designed to work with the overall structural parameters. This would include the cantilevered trusses you referenced.
Homeowner GC's can go thru the same process but the building department is really making it a rigorous process by requiring the homeowner pass a written test to demonstrate some semblance of competence before issuing a permit.
I order my trusses direct from the plant although I would get the same price going thru the lumberyard. I eliminate the middle man and the possibility of compounding errors by dealing with the guy who builds the things and KNOWS what questions to ask if I'm not clear with my requests.
If, after all that, I confirm an order and the plant puts it together, it's mine, right or wrong. The plant did not design the whole structure and has no foolproof method, short of requiring the contractor to provide a set of plans for their review, to assure that the trusses, as built, will be correct for the application. And, that's not their job.
You plant should have a policy in place that says, in effect, you will have a product built to your specifications but we will accept NO responsibility whatsoever if your specifications are incorrect for the application.
Ralph -
Keep in mind that things are a lot different around here. There are no building departments, stamped drawings, or building permits.
The problem is mainly communication. No one takes the time to make 100% sure they know what the other is talking about.
Putting policies in place that will protect us from liability if we can blame someone else for the mistake won't help endear our customers to us. Better to try to prevent problems, which is what I was doing.
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